This package provides a set of very basic abstract classes serving as interfaces to very basic tasks such as:
1. condition checkings (class Checker),
2. data retrieval (class Retriever) and
3. pure workers that perform any kind of actions that do not depend on any kind of input data (class Doer).
Each of these classes is a subclass of class Action which only purpose is to store the object affected by the subclasses action method.